In a vehicle power train system, a damping device, or damper, is needed to transmit power from an engine to a vehicle transmission. The basic function of a damper is to reduce torsional vibration and noise. This is particularly important in a vehicle with a hybrid power system. The damper is of great importance since the large motor inertia may cause excessive impact load being transmitted back to engine and cause engine failure.
Currently there are many designs in which curved coil springs are used to produce damping effect. An example of a current production damper is described in commonly assigned U.S. Pat. No. 6,675,457. The problem with current dampers is that the curved coil springs are expensive to make, leading to a final damper assembly with high costs.
In other designs, straight coil springs are utilized in a spring damping device. In these designs, springs have to be arranged very close to the rotation axial. Such an arrangement reduce torque moment arm radius, leading to a greater load force to be exerted to the springs, which may reduce spring fatigue life. In order to reduce spring loads and to improve fatigue life of springs, the springs have to be arranged to be close to damper outside diameter to maximize torque arm radius.